Mapping, or corridor mapping, have always been performed either by terrestrial mobile mapping technologies or by aerial ones or by combinations thereof, but usually, only one of the two techniques is used.
In small geodata acquisition projects, unmanned aerial systems are used, above all, in military operations, the so-called DDD (dull, dirty and dangerous) missions. An unmanned aerial system is composed of a remotely piloted or unmanned aircraft, a ground control station and a radio data link that lets the unmanned aircraft and the ground control station communicate.
From a technological standpoint, the unmanned aircraft of an unmanned aerial system is an excellent platform to carry photogrammetric, remote sensing and other types of sensors and to carry out aerial sensing missions. As compared to a manned aircraft, an unmanned one is small, lightweight and inexpensive. Moreover, an unmanned aircraft benefits from the current progress in computer and sensor miniaturization.
From a legal—i.e., regulatory—standpoint, depending on the country, unmanned aerial system operations suffer either from lack of regulation or from too strict a regulation. Apart from military and governmental users, like police or firefighters, the use of an unmanned aerial system is many times perceived by the Civil Aviation Authorities and other country or local authorities as a threat to security. Civil Aviation Authorities are concerned about aircraft crashes caused by collision of manned aircraft with unmanned ones. Other authorities are concerned about the misuse of unmanned aerial system technology (terrorism and crime) or about unintentional damage to properties and people (accidents). In general, the larger and heavier the unmanned aircraft is, the more concerns about and restrictions to its operation. There are many concurrent and parallel efforts to develop European, American and worldwide consistent regulations like the Joint Authorities for Rulemaking on Unmanned Systems (JARUS) group with participation of 19 Civil Aviation Authorities as of today.
Most, if not all, existing regulations set three limits to unmanned aerial operations: a weight limit—the so-called Maximum Take Off Weight of the unmanned aircraft,—a distance within line-of-sight (LOS) between the ground control station and the unmanned aircraft—typically a few hundred meters—and a maximum flying height above ground—typically up to 300 m. The “within line-of-sight” or, simply, “LOS restriction” between the ground control station and the unmanned aircraft limits the scope and the productivity of the unmanned aerial system-based geodata acquisition missions as compared to the standard airborne ones. Therefore, apparently, unmanned aerial system-based geodata acquisition and mapping is an area of limited applicability and market.
However, there are more techniques of corridor mapping. For example, railway corridor mapping is usually performed with a terrestrial mobile mapping car or van mounted on a train, trolley or tramcar. Corridor hydro-graphic surveying is also performed many times with a terrestrial mobile mapping car on a small boat. But no simultaneous tandem aerial-terrestrial missions are performed, one of the reasons being that it is almost impossible (airplanes) or too expensive (helicopters) to make an aircraft fly over a terrestrial mobile mapping system at the low speeds of a terrestrial mobile mapping car, between 20 km/h and 60 km/h.
Generally, the missions described above are conducted separately; i.e., no simultaneous aerial-terrestrial missions are performed, thus data acquired in terrestrial mapping missions lack the top view. Analogously, data acquired in aerial mapping missions lack the lateral view of buildings' façades. This leads to duplicate acquisition missions (terrestrial and aerial), a limited, small mission area, or a wrong orientation of the terrestrial vehicle sensors in urban or natural canyons.